Spitzer Follow-up of Extremely Cold Brown Dwarfs Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

14 Aug 2020  ·  Meisner Aaron M., Faherty Jacqueline K., Kirkpatrick J. Davy, Schneider Adam C., Caselden Dan, Gagne Jonathan, Kuchner Marc J., Burgasser Adam J., Casewell Sarah L., Debes John H., Artigau Etienne, Gagliuffi Daniella C. Bardalez, Logsdon Sarah E., Kiman Rocio, Allers Katelyn, Hsu Chih-Chun, Wisniewski John P., Allen Michaela B., Beaulieu Paul, Colin Guillaume, Luca Hugo A. Durantini, Goodman Sam, Gramaize Leopold, Hamlet Leslie K., Hinckley Ken, Kiwy Frank, Martin David W., Pendrill William, Rothermich Austin, Sainio Arttu, Schumann Jorg, Andersen Nikolaj Stevnbak, Tanner Christopher, Thakur Vinod, Thevenot Melina, Walla Jim, Wedracki Zbigniew, Aganze Christian, Gerasimov Roman, Theissen Christopher, Worlds The Backyard, :, Collaboration Planet 9 ·

We present Spitzer follow-up imaging of 95 candidate extremely cold brown dwarfs discovered by the Backyard Worlds: Planet 9 citizen science project, which uses visually perceived motion in multi-epoch WISE images to identify previously unrecognized substellar neighbors to the Sun. We measure Spitzer [3.6]-[4.5] color to phototype our brown dwarf candidates, with an emphasis on pinpointing the coldest and closest Y dwarfs within our sample... The combination of WISE and Spitzer astrometry provides quantitative confirmation of the transverse motion of 75 of our discoveries. Nine of our motion-confirmed objects have best-fit linear motions larger than 1"/yr; our fastest-moving discovery is WISEA J155349.96+693355.2 (total motion ~2.15"/yr), a possible T type subdwarf. We also report a newly discovered wide-separation (~400 AU) T8 comoving companion to the white dwarf LSPM J0055+5948 (the fourth such system to be found), plus a candidate late T companion to the white dwarf LSR J0002+6357 at 5.5' projected separation (~8,700 AU if associated). Among our motion-confirmed targets, five have Spitzer colors most consistent with spectral type Y. Four of these five have exceptionally red Spitzer colors suggesting types of Y1 or later, adding considerably to the small sample of known objects in this especially valuable low-temperature regime. Our Y dwarf candidates begin bridging the gap between the bulk of the Y dwarf population and the coldest known brown dwarf. read more

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Solar and Stellar Astrophysics